Born at Stradbally, Queen's County, Ireland, 1821; died at Sandymount, Dublin, 1905. He entered Carlow College to study for the priesthood, but accompanied his parents to the United States where, completing his studies, he was ordained in 1847, obtaining a mission in the Diocese of St. Louis.

In 1853 he returned to Ireland, was affiliated to the Archdiocese of Dublin and appointed curate in the parish of Sts. Michael and John in the city, one of his fellow curates being the well-known historical scholar, Father Meehan. In 1880 he took charge of the parish of Sandymount and a few years later was made a member of the metropolitan chapter. Always interested in Irish history, especially Irish ecclesiastical history, while in America he wrote an "Abridgment of the History of Ireland" and an "Irish Emigrant's Guide to the United States", besides publishing in the "Boston Pilot" a series of learned papers on St. Malachy, Archbishop of Armagh. After his return to Dublin, he published biographies of St. Laurence O'Toole, St. Dympna, and St. Aengus the Culdee, a "Catechism of Irish History", "Devotions for Confession and Holy Communion", and "Irish American History of the United States", edited Monk Mason's "History of the Irish Parliament", and collected materials for a history of Queen's County. His greatest work was his "Lives of the Irish Saints" (Dublin, 1875—), begun in 1846 and finished shortly before his death.

Dr. Walsh, Archbishop of Dublin, described him as a man who worked so hard at his pastoral duties that men wondered how he could have found time to write anything, and who wrote so much that men wondered how he could have done any missionary work. He never spared himself and was never dismayed by any difficulty; when, in 1898, the manuscript of his "Irish American History" was destroyed, he cheerfully rewrote the volume, an example of courage for a man nearing four score.